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PubMed2004

Sediment treatment with a nitrate-storing compound to reduce phosphorus release.

The application of Fe(III), in combination with sediment oxidation by NO(3)(-), is an accepted procedure to manage stratified eutrophic lakes by controlling the phosphorus release from sediments into overlying water. Depox(R), a newly developed compound, consisting of Fe(III) and NO(3)(-), has a storage effect for NO(3)(-). NO(3)(-) is released slowly, hence the disadvantageous high solubility of NO(3)(-) in water can be retarded. The compound was added to water as a suspension which quickly flocculated and precipitated. Within 3 weeks, NO(3)(-) was desorbed from the Depox(R) compound in deionized water. After application in lakes, the NO(3)(-) availability on the sediment surface was prolonged for 2 months. After treatment, P release from the sediment and microbial metabolism were investigated under laboratory conditions as well as in the mesocosm. P release was almost stopped in both cases during the experiment. SO(4)(2-) consumption was significantly lower after Depox(R) addition, and CH(4) production was completely suppressed by Depox(R) treatment in the laboratory, whereas in the enclosures SO(4)(2-) and also CH(4) concentrations at the sediment water interface did not change significantly between treated enclosures and controls.

Cations↗
PubMed1987

Oxidation of esterified arachidonate by rat liver microsomes.

Rat hepatic microsomal lipids were labeled with [U-14C]arachidonate and were then peroxidized by an NADPH-dependent iron pyrophosphate system. The extent of peroxidation was quantified by malondialdehyde production and arachidonate disappearance. Following peroxidation, the microsomes were centrifuged and the oxidation products were extracted from the supernatant. A linear correlation was found between malondialdehyde production and radioactivity in the supernatant. The pellet was treated with phospholipase A2 to cleave peroxidized products from the phospholipids. Exogenous phospholipase A2 activity was reduced by lipid peroxidation but this was overcome by using a high concentration of the enzyme along with the addition of melittin. The deesterified lipid products from the pellet were extracted and the fragments from the supernatant and the hydrolyzed pellet were separated by reverse-phase HPLC. Several different labeled polar products which coeluted with carbonyl-containing compounds (A285 and hydrazone formation) were found in both the supernatant and the pellet. In addition, many other carbonyl compounds were found which were not arachidonate-derived. The elution pattern of the fragments after 2 and 15 min of peroxidation were qualitatively identical; i.e., no product-precursor relationship was seen. This, along with the observation that peroxidation quickly ceased upon the rapid depletion of NADPH, suggests that propagation did not occur. Finally, the data indicate that cytochrome P-450 is not involved in microsomal lipid peroxidation since product formation is unaffected by the presence of carbon monoxide (80%) and no oxidation of phospholipid arachidonate occurs in the absence of iron.

Animals↗
PubMed2000

The role of ferrioxamine E in pre-enrichment medium for determining Salmonella in environmental samples according to ISO method.

The effect of a siderophoric compound, ferrioxamine E, in the pre-enrichment broth on determining of Salmonella infantis in environmental samples was tested with combination of various pre-enrichment times and enrichment temperatures of 37 and 43 degrees C. Ferrioxamine E slightly improved the determination efficiency of this bacterium but the pre-enrichment time could not be reduced below 17 hours. The enrichment temperature of 43 degrees C was better than of 37 degrees C. The mixing ratios of 1:100 or 1:1000 for samples and pre-enrichment broth were more successful than the ratio of 1:10 as recommended by ISO.

Animals↗
PubMed1998

Characterization of the cytoprotective action of peroxynitrite decomposition catalysts.

The formation of the powerful oxidant peroxynitrite (PN) from the reaction of superoxide anion with nitric oxide has been shown to be a kinetically favored reaction contributing to cellular injury and death at sites of tissue inflammation. The PN molecule is highly reactive causing lipid peroxidation as well as nitration of both free and protein-bound tyrosine. We present evidence for the pharmacological manipulation of PN with decomposition catalysts capable of converting it to nitrate. In target cells challenged with exogenously added synthetic PN, a series of metalloporphyrin catalysts (5,10,15,20-tetrakis(2,4,6-trimethyl-3, 3-disulfonatophenyl)porphyrinato iron (III) (FeTMPS); 5,10,15, 20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) (FeTPPS); 5,10, 15,20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron (III) (FeTMPyP)) provided protection against PN-mediated injury with EC50 values for each compound 30-50-fold below the final concentration of PN added. Cytoprotection was correlated with a reduction in the level of measurable nitrotyrosine. In addition, we found our catalysts to be cytoprotective against endogenously generated PN in endotoxin-stimulated RAW 264.7 cells as well as in dissociated cultures of hippocampal neurons and glia that had been exposed to cytokines. Our studies thus provide compelling evidence for the involvement of peroxynitrite in cytokine-mediated cellular injury and suggest the therapeutic potential of PN decomposition catalysts in reducing cellular damage at sites of inflammation.

Animals↗
PubMed1979

On the mechanism of Verhoeff's elastica stain: a convenient stain for myelin sheaths.

Verhoeff (1908) recommended an iron-hematein formula containing Lugol's solution for demonstration of elastic tissue; sections are differentiated until desired staining patterns are obtained. Verhoeff's stain colored a variety of tissue structures and showed higher substantivity for myelin sheaths than for elastin. Addition of HCL or omission of Lugol's solution decreased or abolished coloration of pseudo-elastica and thus enhanced selectivity for elastin. Substitution of Fe++ for Fe+++ abolished dye binding by elastin. A review of chemical data indicated interaction of components of Lugol's solution with the dye. Hematein and Fe+++ form a variety of cationic, anionic and non-ionic chelates; the ratio of these compounds changes with time. Dye binding apparently occurs mainly via van der Waals forces and hydrogen bonds. Verhoeff's elastica stain is definitely not specific for elastin and is inferior to orcein and resorcin-fuchsin because of the required differentiation with its inherent bias to produce patterns which conform to expectations. However, Verhoeff's elastica stain is far superior to other metal-hematein technics for myelin sheaths. The combined Verhoeff-picro-Sirius Red F3BA stain can be performed in 30 min and does not require differentiation. It is therefore suggested to reclassify Verhoeff's elastica stain as a method for myelin sheaths.

Aorta↗
PubMed2005

XAS evidence of As(V) association with iron oxyhydroxides in a contaminated soil at a former arsenical pesticide processing plant.

The molecular-level speciation of arsenic has been determined in a soil profile in the Massif Central near Auzon, France that was impacted by As-based pesticides by combining conventional techniques (XRD, selective chemical extractions) with X-ray absorption spectroscopy (XAS). The arsenic concentration is very high at the top (>7000 mg kg(-1)) and decreases rapidly downward to a few hundreds of milligrams per kilogram. A thin layer of schultenite (PbHAsO4), a lead arsenate commonly used as an insecticide until the middle of the 20th century, was found at 10 cm depth. Despite the occurrence of this As-bearing mineral, oxalate extraction indicated that more than 65% of the arsenic was released upon dissolution of amorphous iron oxides, suggesting a major association of arsenic with these phases within the soil profile. Since oxalate extraction cannot unambiguously distinguish among the various chemical forms of arsenic, these results were confirmed by a direct in situ determination of arsenic speciation using XAS analysis. XANES data indicate that arsenic occurs mainly as As(V) along the soil profile except for the topsoil sample where a minor amount (7%) of As(III) was detected. EXAFS spectra of soil samples were fit by linear combinations of model compounds spectra and by a shell-by-shell method. These procedures clearly confirmed that As(V) is mainly (at least 80 wt %) associated with amorphous Fe(III) oxides as coprecipitates within the soil profile. If any, the proportion of schultenite, which was evidenced by XRD in a separate thin white layer, does not account for more than 10 wt % of arsenic in soil samples. This study emphasizes the importance of iron oxides in restricting arsenic dispersal within soils following dissolution of primary As-bearing solids manufactured for use as pesticides and released into the soils.

Arsenic↗
PubMed1993

The production of antifungal volatiles by Bacillus subtilis.

A strain of Bacillus subtilis which produces an antibiotic metabolite was also found to produce a volatile compound(s) which was antifungal to Rhizoctonia solani and Pythium ultimum. Growth of the fungi was severely impaired in the presence of the volatiles and physiological abnormalities of the hyphae were observed, including hyphal distortion and vacuolation. A range of media were tested for volatile production and potato dextrose agar (PDA) was found to be the most active. Temperature had a considerable effect on antifungal volatile activity with the greatest inhibition occurring at 30 degrees C. Addition of iron (III) chloride to Sabouraud's glucose agar (SGA) also enhanced the antifungal effect. The volatiles were found to be water soluble and remained active when trapped in SGA.

Antifungal Agents↗
PubMed1983

Iron supply to Escherichia coli by synthetic analogs of enterochelin.

Synthetic analogs of enterochelin (enterobactin) were tested for their ability to support the growth of Escherichia coli K-12 under iron-limiting conditions. The cyclic compound MECAM [1,3,5-N.N'; N"-tris-(2,3-dihydroxybenzoyl)-triamino-methylbenzene] and its N-methyl derivative Me3MECAM promoted growth, whereas the 2,3-dihydroxy-5-sulfonyl derivatives MECAMS and Me3MECAMS were inactive. The same results were obtained with TRIMCAM [1,3,5-tris(2,3-dihydroxybenzoylcarbamido)-benzene] and TRIMCAMS (the 2,3-dihydroxy-5-sulfonyl derivative of TRIMCAM). However, the sulfonic acid-containing linear compound LICAMS [1,5,10-N,N', N"-tris(5-sulfo-2,3-dihydroxybenzoyl)-triaza-decane] supported growth. In contrast, LIMCAMC, in which the sulfonyl groups at the five position of LICAMS are replaced by carboxyl groups at the four position, was inactive. The uptake of the active analogs required the functions specified by the fepB, fesB, and tonB genes. Surprisingly, growth promotion of mutants lacking the enterochelin receptor protein in the outer membrane was observed. Only MECAM protected cells against colicin B (which kills cells after entering at the enterochelin uptake sites) and transported Fe3+ at about half the enterochelin rate.

Biological Transport↗
PubMed1989

Middle cerebral artery occlusion in rats studied by magnetic resonance imaging.

Ischemia due to middle cerebral artery occlusion was studied in 29 rats from 1 to 24 hours after occlusion using magnetic resonance imaging. Images were made before and after the injection of a superparamagnetic iron oxide compound, AMI-25. Subtraction images demonstrated the region of perfusion deficit as early as 1 hour after occlusion, earlier than conventional T2-weighted images. The area of altered perfusion detected by this technique (subtraction imaging after AMI-25 administration) correlated with that demonstrated by iodoantipyrine autoradiography. Since this magnetic resonance technique can be used to serially estimate the location and size of the ischemic area, the technique can be an important adjunct to metabolic studies of focal ischemia using magnetic resonance spectroscopy. The technique may have clinical applications as well.

Animals↗
PubMed2006

Small-molecule screening identifies the selanazal drug ebselen as a potent inhibitor of DMT1-mediated iron uptake.

HEK293T cells overexpressing divalent metal transporter-1 (DMT1) were established to screen for small-molecule inhibitors of iron uptake. Using a fluorescence-based assay, we tested 2000 known bioactive compounds to find 3 small molecules that potently block ferrous iron uptake. One of the inhibitors, ebselen, is a seleno compound used in clinical trials as a protective agent against ischemic stroke. Ebselen inhibited Fe(II) uptake (IC(50) of approximately 0.22 microM), but did not influence Fe(III) transport or DMT1-mediated manganese uptake. An unrelated antioxidant, pyrrolidine dithiobarbamate (PDTC), also inhibited DMT1 activity (IC(50) of approximately 1.54 microM). Both ebselen and PDTC increased cellular levels of reduced glutathione. These observations indicate that Fe(II) transport by DMT1 can be modulated by cellular redox status and suggest that ebselen may act therapeutically to limit iron-catalyzed damage due to transport inhibition.

Antioxidants↗
PubMed2005

New magnetic nano-absorbent for the determination of n-octanol/water partition coefficients.

A novel and generic miniaturization methodology for the determination of partition coefficient values of organic compounds in n-octanol/water by using magnetic nanoparticles is, for the first time, described. We have successfully designed, synthesised and characterised new colloidal stable porous silica-encapsulated magnetic nanoparticles of controlled dimensions. These nanoparticles absorbing a tiny amount of n-octanol in their porous silica over-layer are homogeneously dispersed into a bulk aqueous phase (pH 7.40) containing an organic compound prior to magnetic separation. The small size of the particles and the efficient mixing allow a rapid establishment of the partition equilibrium of the organic compound between the solid supported n-octanol nano-droplets and the bulk aqueous phase. UV-vis spectrophotometry is then applied as a quantitative method to determine the concentration of the organic compound in the aqueous phase both before and after partitioning (after magnetic separation). logD values of organic compounds of pharmaceutical interest (0.65-3.50), determined by this novel methodology, were found to be in excellent agreement with the values measured by the shake-flask method in two independent laboratories, which are also consistent with the literature data. It was also found that this new technique gives a number of advantages such as providing an accurate measurement of logD value, a much shorter experimental time and a smaller sample size required. With this approach, the formation of a problematic emulsion, commonly encountered in shake-flask experiments, is eliminated. It is envisaged that this method could be applicable to the high throughput logD screening of drug candidates.

Ferric Compounds↗
PubMed2001

Cytochrome b(5) plays a key role in human microsomal chromium(VI) reduction.

The reduction of chromium(VI) to Cr(III) results in the formation of reactive intermediates that contribute to the cytotoxicity, genotoxicity, and carcinogenicity of Cr(VI)-containing compounds. Previous studies suggest that human microsomal Cr(VI) reduction likely proceeds through cytochrome b(5). In order to better understand Cr(VI) toxicity in humans, the role of cytochrome b(5) in combination with P450 reductase was examined in the reductive transformation of Cr(VI). Proteoliposomes containing human recombinant cytochrome b(5) and P450 reductase were constructed. The ability of P450 reductase to mediate efficient electron transfer from NADPH to cytochrome b(5) was confirmed by spectral analysis. The NADPH-dependent Cr(VI) reduction rate mediated by proteoliposomes was then compared to that of human microsomes. When these rates were normalized to equivalent cytochrome b(5) concentrations, the NADPH-dependent Cr(VI) reduction rates mediated by human microsomes were essentially identical to those for proteoliposomes containing cytochrome b(5) plus P450 reductase. Proteoliposomes containing only P450 reductase or cytochrome b(5) exhibited poor Cr(VI) reducing capabilities. Since it had been previously shown that trace amounts of iron (Fe) could dramatically stimulate microsomal Cr(VI) reduction, the ability of Fe to stimulate Cr(VI) reduction by proteoliposomes was examined. Both ferric chloride (FeCl(3)) and ferric adenosine-5'-diphosphate (FeADP) were shown to stimulate Cr(VI) reduction; this stimulation could be abolished by the addition of deferoxamine, a specific Fe(III) chelator. The NADPH-dependent reduction rates of various ferric complexes by proteoliposomes were sufficient to account for the increased Cr(VI) reduction rates seen with the addition of FeCl(3) or FeADP. Cr(V) was detected by electron paramagnetic resonance (EPR) spectroscopy as a transient intermediate formed during NADPH-dependent Cr(VI) reduction mediated by proteoliposomes containing cytochrome b(5) and P450 reductase. Overall, cytochrome b(5) in combination with P450 reductase can account for the majority of the NADPH-dependent Cr(VI) reduction seen with human microsomes.

Adenosine Diphosphate↗
PubMed2004

On the Mössbauer spectra of isopenicillin N synthase and a model (FeNO)7 (S = 3/2) system.

We have carried out a series of density functional theory (DFT) calculations to predict the 57Fe Mössbauer quadrupole splittings (DeltaEQ) and isomer shifts (deltaFe) for the nitrosyl complex of isopenicillin N synthase with the substrate delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-valine (IPNS.ACV.NO) and an {FeNO}7 (S = 3/2) model system, FeL(NO)(N3)2 (L = N,N',N' '-trimethyl-1,4,7-triazacyclononane). B3LYP predictions on the model compound are in almost exact agreement with experiment. The same DFT methods did not enable the prediction of the experimental DeltaEQ and deltaFe results for IPNS.ACV.NO when using the experimental protein crystal structure but did permit good predictions of DeltaEQ, deltaFe, and the asymmetry parameter (eta) when using a fully optimized structure. This optimized structure also enabled good predictions of the Mössbauer spectra of the photodissociation product of IPNS.ACV.NO. Mulliken and natural bonding orbital (NBO) spin density analyses indicate an electronic configuration of FeII (S = 2) anti-ferromagnetically coupled to NO (S = 1/2) in the protein as well as in the model system and the geometry optimized structure helps explain part of the enzyme reaction.

Binding Sites↗
PubMed1994

Different oxidative pathways of isonicotinic acid hydrazide and its meta-isomer, nicotinic acid hydrazide.

1. Superoxide was generated during the auto-oxidation of the antituberculous drug, isonicotinic acid hydrazide (INH), but not with its meta-isomer, nicotinic acid hydrazide (NH). During Fe(3+)-stimulated oxidation of INH and NH, aromatic hydroxylation occurred which was inhibited by the chelating agent, phytic acid. 2. A mixture of myeloperoxidase (MPO) and a hydrazide induced formation of compound III (oxyperoxidase) and aromatic hydroxylation which was stimulated by phytic acid. INH was considerably more potent than NH. 3. Co-oxidation of a hydrazide and thyroxine (T4) in the MPO system resulted in the formation of a pink-coloured product (maximum absorbance at 504 nm) which was more stable with NH than with INH. 4. The hydrazides and Cl- acted synergistically on MPO haem modification when co-oxidised in the MPO-H2O2 system. INH was more destructive than NH. 5. The different oxidative pathways of the hydrazides are consistent with the fact that an acyl intermediate of INH, unlike that of NH, is resonance stabilized.

Carcinogens↗
PubMedDate not supplied

Nitration and hydroxylation of phenolic compounds by peroxynitrite.

The kinetics and products of the reaction of peroxynitrite with the phenolic compounds phenol, tyrosine, and salicylate were studied as a function of pH. All reactions are first-order in peroxynitrite and zero-order in the phenolic compound. Relative to the hydroxyl group, electrophilic substitution in the 2- and 4-positions (if available) leads to hydroxylated and nitrated products. The total yield of the products is proportional to the concentration of peroxynitrite. The sum of the rates of hydroxylation and nitration of phenol, determined by the stopped-flow technique, is approximately equal to the rate constant for the isomerization of peroxynitrite to nitrate. The rate vs pH profiles of the nitration and hydroxylation reactions parallel the yield vs pH profile with nitration maxima at pH 1.8 and 6.8, while hydroxylation is dominant between these two pH values. The activation energies for both hydroxylation and nitration are 18.8 +/- 0.3 kcal mol-1, identical to that of the isomerization of peroxynitrite to nitrate. Ethanol decreases the yield of hydroxylation, but has less effect on the nitration. The rate of reaction in the presence of metal complexes is first-order in metal complex and peroxynitrite and zero-order in the phenolic compound. The enhancement of the nitration of phenol by Fe(III)-edta and -nta is pH-dependent, with a maximum near pH 7, while Fe(III)-citrate, Cu(II)-edta, and CuSO4 affect the nitration much less. The second-order rate constants for Fe(III)-edta at pH 4.8 and 7.2 are 1.4 x 10(3) and 5.5 x 10(3) M-1 s-1, respectively, at 25 degrees C. The activation energies for the nitration reaction in the presence of Fe(III)-edta are 11.5 and 12.2 kcal mol-1 at pH 4.8 and 7.2, respectively. The nitration of tyrosine and salicylate by peroxynitrite is maximally enhanced by Fe(III)-edta.

Copper↗
PubMed1977

Fe(III)-EDTA complex as iron fortification.

Fe(III)-EDTA as iron fortification presents several advantages over the other iron salts previously used including ferrous sulfate. This iron compound exchange completely with vegetable food iron in the lumen of the gut but with the characteristics that the absorption from both, extrinsic and intrinsic food iron, is higher than that expected from other iron salfs. The comparison between the iron absorption from Fe(III)-EDTA and ferrous sulfate as iron fortification indicates that the absorption form EDTA is about twice as high than that observed from ferrous sulfate. The data indicates that only 10 to 15 mg of iron as Fe(III)-EDTA as iron fortification would be necessary to prevent iron deficiency anemia in population relying their subsistence of vegetable food only and free of parastic infection producing blood loss.

Absorption↗
PubMed1994

Inflammatory and phagocytic response to experimental Campylobacter jejuni infection in mice.

After intraperitoneal inoculation with Campylobacter jejuni BALB/c, Swiss and DBA mice show a peritoneal inflammatory response of different intensity. Only BALB/c mice have a strong peritoneal response. Simultaneous intraperitoneal inoculation of C. jejuni plus FeCl3 increase both inflammatory response and phagocytic activity in Swiss mice, without production of diarrhea. Some thermostable compounds of C. jejuni have a very strong chemotactic activity against peritoneal cells of mice, whereas a diffusible, thermolabile and glutaraldehyde-resistant factor has an inhibitory effect over murine peritoneal cell phagocytosis. Bactericidal activity of peritoneal cells increased after in vitro re-challenge with C. jejuni. Bacteremia is present in all the mice strains tested, but the clearance is quick in DBA and slow in BALB/c and Swiss mice. These experiments confirm that in mice, peritoneal non-specific mechanisms of defense, such as macrophages, play an important role in order to control C. jejuni infection.

Animals↗
PubMed1994

Interaction domain for the reaction of cytochrome c with the radical and the oxyferryl heme in cytochrome c peroxidase compound I.

Site-directed mutants of cytochrome c peroxidase (CcP) were created to modify the interaction domain between CcP and yeast iso-1-cytochrome c (yCC) seen in the crystal structure of the CcP-yCC complex [Pelletier & Kraut (1992) Science 258, 1748-1755]. In the crystalline CcP-yCC complex, two acidic regions of CcP contact lysine residues on yCC. Mutants E32Q, D34N, E35Q, E290N, and E291Q were used to examine the effect of converting individual carboxylate side chains in the acidic regions to amides. The A193F mutant was used to test the effect of introducing a phenyl moiety at the point of closest contact between CcP and yCC in the crystal structure. Stopped-flow experiments carried out in 310 mM ionic strength buffer at pH 7 revealed that yCC initially reduced the indole radical on Trp-191 of the parent CcP compound I with a bimolecular rate constant ka = 2.5 x 10(8) M-1 s-1. A second molecule of yCC subsequently reduced the oxyferryl heme of compound II with a rate constant kb = 5 x 10(7) M-1 s-1. The bimolecular rate constants ka and kb were affected in parallel by each mutation examined. CcP mutants D34N and E290N that are closest to a complementary yCC lysine residue in the crystalline CcP-yCC complex gave the lowest values for ka and kb, which were 25-50% of the values of the CcP parent. Mutants E32Q and E291Q that are removed from the interaction domain gave the same ka and kb values as the CcP parent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗